An older pic of our BB El Camino we've had since the mid-'80s, this has the same GM suspension as your '72 Cutlass:
Suspension was done in the low-budget style you are interested in, and similar to what Joe Padavano outlines above. There was a little cutting and welding. It worked great, beyond what I would have expected, and does drive like a newer, smaller car than what it is. My family had a '72 350 Chevelle new, which was a lurching bouncing understeering pig...this car is
nothing like that.
Front spindles are the taller GM style, from a '70s Cadillac Seville w/ 12" 4-wheel disc option and 1LE Camaro rotors. The a-arms were modified to accept these and increase the caster to 6 degrees, catalog parts are available for this if you don't do fabrication. Springs and front swaybar are original SS-396 stuff, and bushings are urethane. Very important to all this working well for cheap was bigger shocks (not more expensive ones), from a '70s Dodge half-ton truck, the a-arm holes had to be ground out a little bit. Steering box is '80s Cutlass, which is not the total hot ticket but faster than stock.
The rear swaybar is also GM, because it acts directly on control arm angles and not from partway up, the rr is normally smaller than the front (proof you have it right comes when the handling is about neutral). Springs are again stock, with stiffer shocks. Control arms are boxed upper and lower per original SS, as mentioned above while this makes them stiffer it also defeats their ability to twist so compliant bushing must be used (and on this car the urethane/rubber bushing combination works fine for normal driving but wants to hop at the drag strip and needs something different if used that way). 12" rear discs are from the same Cadillac as the front, requiring a spacer ring, slotting the wheel stud holes and shimming the diff c-clips to reduce side-to-side play.
Wheels are stock SS, modified from 14x7 to 15x8 (that used to be a big job but now you can buy them that way) and tires are 275-50R15s.
The frame is boxed per normal El Camino, has original SS rear control-arm bracing (an add-on) and an extra rectangle-tube crossmember there, and up front there is bracing from the front crossmember to under the firewall such as on '73-77 cars, and various other reinforcing to eliminate cracking such as normally happens with big-block cars.
Maybe this all cost $500...probably less...but of-course was some work. You could buy it all for under two grand now I imagine.
I used this with a mild 396 and a Richmond 5-speed manual, for probably 100K 'til the rod bearings wore out. What a great driver, it did everything well (albeit at 14 mpg but that wasn't the question here). It sits in the barn, waiting for a fresh motor, new paint and it's turn to come around again.